Plastic closure device for tubular bags

ABSTRACT

A plastic closure device ( 1 ) must be welded by means of ultrasound onto a tubular bag ( 2 ) consisting of a multilayer plastic film ( 20 ). For this purpose, an energy introduction arrangement ( 182 ) on the underside ( 180 ) of a flange ( 18 ) is proposed, in which at least one energy conduction rib ( 183 ) concentric with the outer edge ( 181 ) of the flange is present, as well as a plurality of outwardly-directed energy conduction ribs ( 184 ). These energy conduction ribs can intersect in the region of intersection ( 185 ) or they can be interrupted in the region of intersection.

BACKGROUND OF THE INVENTION

The present invention relates to a plastic closure device for tubular bags having a bottom part comprising a spout and a flange with a flange underside, an energy introduction arrangement, which is connectable to a plastic layer by means of ultrasonic welding, being arranged on said flange underside, wherein the energy introduction arrangement has at least one energy-conducting rib which extends concentrically with respect to the flange rim.

Plastic closure devices for tubular bags, which are mostly referred to as pouches in industry terminology, are known in various configurations. The plastic closure devices usually comprise a bottom part, which is directly fastened on the tubular bag, and a screw cap, which is detachably fastened on the bottom part, for closing a spout in the bottom part. For the purpose of fastening the plastic closure devices, a flange belonging to the bottom part is fixedly fastened in an integrally bonded manner on the plastic film material of the tubular bag using ultrasonic welding. This welded joint is formed either directly between the flange underside and the plastic film of the tubular bag, or between the flange underside and a plastic patch which closes a stamped opening in the plastic film of the tubular bag.

Such solutions are shown, for example, in the document JP-2000016453, two energy-conducting ribs extending concentrically with respect to the flange rim being shown here, whereas the document JP-2000344264 shows a like plastic closure device for a tubular bag wherein only one energy-conducting rib, which extends concentrically with respect to the rim of the flange, is present.

The design of the energy-conducting ribs always has the objective of achieving the best possible connection between the flange of the bottom part of the plastic closure device and the tubular bag. The results of such weldings are tested. Presently, two different types of tests are considered in this context, namely in the first instance a test referred to as tensile test in which the attempt is made to tear off the flange of the plastic closure device perpendicular to the plane created by the spread-out film. The second test which is presently customary is referred to as twist test; here, the film onto which the plastic closure device is welded is clamped, and a torque is applied to the plastic closure device until destruction and/or detachment of the plastic closure device from the plastic film of the tubular bag occurs.

SUMMARY OF THE INVENTION

Purely by coincidence, the applicant has determined that in the case of pairs of test specimens which had passed both described tests to absolute satisfaction, it was possible to place a finger nail under the flange using comparatively little force and to subsequently separate the closure from the plastic film with comparative ease by tilting the closure.

Having further investigated this hitherto unknown phenomenon, it was determined that this phenomenon was only encountered in the case of tubular bags made from multilayer plastic films. Multilayer films having the following construction were tested: PP—AL—PE and PP—PETSiOx—PE. In the case of all these multilayer plastic films the tests showed that a delamination practically occurs in the course of said tilting tests, similar to an aluminum foil which can be removed from a plastic cup onto which it has been welded. Likewise, films which additionally have a cardboard layer display the same problem. Many elaborate test series were carried out in order to achieve improved results. The solution found is per se extremely easy to implement, and it is thus all the more surprising that it leads to the desired result. A physical explanation cannot be provided with confidence from this end.

It is thus the object of the present invention to provide an improved welded joint between a plastic closure device and a tubular bag consisting of multilayer plastic films. This object is achieved by a tubular bag consisting of multilayer plastic films, having a plastic closure device comprising a bottom part having a spout and a flange, an energy introduction arrangement, which is connected to a plastic layer of the tubular bag, being arranged on the flange underside of said flange, wherein the energy introduction arrangement has at least one energy-conducting rib which extends concentrically with respect to the peripheral flange rim and said energy introduction arrangement is characterized by the at least one concentric energy-conducting rib intersecting a multiplicity of outwardly oriented energy-conducting ribs which extend as far as the peripheral flange rim, or by at least one virtual intersecting region being provided.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantageous embodiments of the subject matter of the invention emerge from the dependent claims, and their significance and operation is explained in the following description with reference to the attached drawings, in which:

FIG. 1 shows a partial view of a plastic closure device which is welded onto a multilayer plastic film;

FIG. 2 serves to explain the construction of the plastic films which are of interest in this context, and

FIG. 3 shows a view from below onto a plastic closure device, highlighting the flange underside of this plastic closure device.

FIG. 4 is a symbolic illustration of the design of a tensile testing arrangement, while

FIG. 5 also symbolically illustrates a twist testing arrangement, and finally

FIG. 6 shows what is referred to as a peel testing arrangement in which the tilting torque is determined which is necessary for the separation of the plastic closure device from the multilayer plastic film of a tubular bag.

DETAILED DESCRIPTION

The plastic closure device, which is identifiable in its entirety in a lateral view in FIGS. 5 and 6 and is illustrated from below in FIG. 3, is collectively referred to with the reference sign 1. This plastic closure device 1 is intended to be attached to a tubular bag 2. Here, the tubular bag 2 may be completely aseptically closed or have a stamped opening which is closed by the plastic closure device 1. The design of the tubular bag 2 is irrelevant in this context. For this reason, the illustration of the tubular bag 2 in its entirety has been dispensed with. It is only in FIG. 6 that the tubular bag 2 is symbolically illustrated in a partial view.

In FIG. 1, a partial view of the plastic closure device 1 is partially visible. Here, only the bottom part 10 of the plastic closure device 1 has been illustrated. The plastic closure device 1, however, at least also comprises an upper part 11 which is usually implemented as a screw cap 12. This screw cap 12 has a warranty seal strip 13, which is located below and flush with the jacket wall of the screw cap 12 and connected to the latter via a specified rupture location bridge. The bottom part 10 comprises a spout 14 which is formed as a cylindrical tube section. The spout 14 has an external thread 15 for the screw connection with an internal thread, not illustrated here, of the screw cap 12. An encircling retaining collar 16, which is formed at a distance above a flange 18 formed on the periphery of the spout 14, is located below the external thread 15. This retaining collar 16 serves for the form-fitting connection with a corresponding molding on the warranty seal strip 13. In addition, retaining cams 17 are also visible which are capable of reaching between the screw cap 12 and the warranty seal strip 13.

In the case where the tubular bag 2 is formed as an aseptically closed tubular bag, the plastic closure device 1 has to be additionally provided with an opening device 19. Such an opening device is visible in FIG. 3. The opening device 19 is commonly screwably mounted in the spout 14. This substantially refers to a cylindrical tube section which is open at both ends and which, on its lower end which in the assembled state faces the flange 18 of the bottom part 10, has a cutting edge 192 which is provided with teeth 191. The opening device on its inside has at least one dog 193 with which a dog, not visible here, in the screw cap 12 engages and, in the course of the initial opening, initiates a screwing motion of the opening device 19 and thus cuts open the multilayer plastic film of the tubular bag 2.

The tubular bag 2 consists of a multilayer plastic film. This multilayer plastic film is shown in FIG. 2 in magnification as a cut specimen. The multilayer plastic film is collectively referred to with the reference sign 20. The construction of this plastic film is as follows:

Outermost is a plastic layer 21. This is connected to a barrier layer 23 by an adhesive layer 22. Said barrier layer, in turn, is connected to an inner plastic layer 24.

The outer plastic layer preferably consists of a polypropylene (PP), in particular of an ortho-polypropylene (oPP). Using the barrier layer 23, corresponding light protection is achieved, and said barrier layer must be made from aluminum (AL). In the event that such light protection is not necessary or not desirable, a polyethyleneterephthalate with embedded silicon (PETSiOx) may be used in its place. The innermost plastic layer 24 usually consists of a polyethylene. The thicknesses of the layers of material illustrated here are intended only as relative indications which, however, need not be binding. It is, however, advantageous to choose the outer polypropylene layer to be as thin as possible in order to maintain the flexibility of the tubular bag.

The actual substance of the invention is evident in FIG. 3. Here, the flange underside 180 of the flange 18 is fully visible. The flange 18 is delimited by an outer rim 181. A multiplicity of energy-conducting ribs are located on the flange underside. The collectivity of all energy-conducting ribs is described as energy introduction arrangement 182.

The energy introduction arrangement 182 consists on the one hand of an energy-conducting rib 183 which extends concentrically with respect to the outer rim of the flange 181 and which is known per se. This at least one concentric energy-conducting rib 183 intersects a multiplicity of energy-conducting ribs 184, which extend and are oriented outwardly. These energy-conducting ribs 184, which extend and are oriented outwardly, extend as far as the peripheral flange rim 181.

Instead of the at least one energy-conducting rib 183, which extends concentrically with respect to the outer rim of the flange 181, a plurality of concentric energy-conducting ribs 183, in particular two or three, may also be provided. The energy-conducting ribs 184, which extend and are oriented outwardly, are preferably arranged radially oriented. The energy-conducting ribs may, however, also deviate from the radial direction and be arranged extending and oriented outwardly. The person skilled in the art will choose the number of the different energy-conducting ribs and/or the density of their arrangement such that sufficient material melts in order to achieve a flawless welding, but on the other hand also optimize this such that no unduly excessive amount of material needs to be softened, as this would automatically be associated with an increased consumption of energy. In order not to have, for example, all too excessive concentrations of softened material in certain locations, the intersecting regions 185 of the energy-conducting ribs 183, 184 may be developed differently. At 185, the concentrically extending energy-conducting rib and the radially extending energy-conducting rib actually intersect, whereas at 186, the concentrically extending energy-conducting rib is interrupted in the thus virtual intersecting region 186, whereas the radially extending energy-conducting rib extends in a continuous manner. The intersecting region may alternatively also be formed such that the concentrically extending energy-conducting rib is continuous whereas the radially outwardly extending energy-conducting rib is interrupted in this also virtual intersecting region 187. As mentioned, this prevents an unnecessary and undesirable local concentration of molten material.

FIG. 4 now shows in a symbolic manner a testing arrangement for a tensile test. Here, that force is measured which is required to tear off the plastic closure device, which is welded to a multilayer plastic film, from said film. This test is usually referred to as tensile test.

In FIG. 5, a multilayer plastic film 20 which is held in a planar manner can be seen, a torque being applied to the plastic closure device 1 at the same time. Here, the torque which is required to cause a shearing-off of the flange from the multilayer plastic film is determined. Lastly, a tilting test is illustrated only symbolically in FIG. 6. How such a tilting test should be carried out in reality has not yet been determined at this end. The tests to date have been conducted purely manually and subjectively. In said FIG. 6, the tubular bag 2 is at least partially illustrated.

At this end, it can only be speculated why the results based on the new energy-conducting rib arrangement according to the invention are surprisingly substantially better. In the course of ultrasonic welding, a sonotrode presses against the surface of the flange of the plastic closure device. As a result of the ultrasonic oscillations created, friction is generated between the film and the energy-conducting ribs, said friction leading to the melting of the plastic. Until now, it has been assumed that the molten material would uniformly flow in all directions under the pressure of the sonotrode. In order to have to move as little mass as possible and thus to also have to use as little energy as possible, the thickness of the flange has been continuously reduced. As a result, a concentration of material towards the center takes place. One therefore proceeds from the assumption that stronger oscillations occur in the peripheral region of the flange than in the central region of the flange. As a result, this favors a flow in the direction of the center. In order to nevertheless achieve a flawless welding in spite of this phenomenon, the present arrangement of the energy-conducting ribs has been found by testing.

In the tilting and/or peeling tests as illustrated in FIG. 6, it has been determined that the majority of all plastic closure devices which have been applied to such tubular bags using the traditional solutions for the arrangement of the energy-conducting ribs can tilt off and/or peel off using modest force. In this context it was demonstrated that the outer plastic film layer 21 indeed mostly remains adhered to the flange, but is practically peeled off from the adhesive layer 22 or the barrier layer 23. It is, therefore, quite possible that in the case of the arrangement of the energy-conducting ribs which has been usual up to now, namely arrangements in which only concentrically extending energy-conducting ribs are present, the actual melting process occurs over a smaller area and the flow of the plastic is substantially slower than hitherto expected, or certain concentrations of energy occur which lead to said peeling effect. In any case, this problem has been solved by the arrangement of the energy-conducting ribs according to the invention. 

1. A tubular bag apparatus comprising a tubular bag (2) consisting of multilayer plastic film, a plastic closure device (1) comprising a bottom part (10) having a spout (14) and a flange (18), and an energy introduction arrangement (182), which is connected to a plastic layer of the tubular bag (2), being located on a flange underside (180) of said flange, wherein the energy introduction arrangement (182) has at least one energy-conducting rib (183) which extends concentrically with respect to a peripheral flange rim, characterized in that the at least one concentric energy-conducting rib (183) intersects a multiplicity of energy-conducting ribs (184) which extend and are oriented outwardly and which extend as far as the peripheral flange rim (181).
 2. The tubular bag apparatus as claimed in claim 1, characterized in that the outwardly extending energy-conducting ribs (184) are radially outwardly oriented and intersect the at least one concentric energy-conducting rib (183).
 3. The tubular bag apparatus as claimed in claim 1, characterized in that the energy-conducting ribs (184) have a rounded cross section having a radius (r) on their encircling round ends and subsequently merge with outwardly inclined flanges (18), with maximum elevations forming an approximately punctiform support.
 4. The tubular bag apparatus as claimed in claim 2, characterized in that a flange top side is freely accessible above a region in which the energy-conducting ribs (183) are located.
 5. The tubular bag apparatus as claimed in claim 3, characterized in that flanks of the energy-conducting ribs (183), which flanks are evident in cross section, enclose an angle (α) of 50° to 70°.
 6. The tubular bag apparatus as claimed in claim 1, characterized in that round ends of the energy-conducting ribs (183) are, when viewed in cross section, approximately punctiform supports of the energy-conducting ribs.
 7. The tubular bag apparatus as claimed in claim 1, characterized in that a height (h) of the energy-conducting ribs (183) measures between 0.2 and 0.4 mm.
 8. The tubular bag apparatus as claimed in claim 1, characterized in that the underside is curved toward a flange top side in a peripheral region (Y) which is adjacent to an outer energy-conducting rib (184).
 9. The tubular bag apparatus as claimed in claim 1, characterized in that the energy-conducting ribs (184), which extend and are oriented outwardly, are interrupted in an intersecting region (185) and are spaced at a distance which is equal to at least a width of one energy-conducting rib from the at least one concentrically extending energy-conducting rib (183) in a virtual intersecting region (185).
 10. The tubular bag apparatus as claimed in claim 1, characterized in that the at least one concentrically extending energy-conducting rib (183) is interrupted in a virtual intersecting region (185).
 11. The tubular bag apparatus as claimed in claim 1, characterized in that the tubular bag (2) consists of a multilayer plastic film (20) which has one of the following combinations of layers: PP—AL—PE; PP—MPET—PE; and PP—PETSiOx—PE.
 12. The tubular bag apparatus as claimed in claim 1, characterized in that the plastic closure device (1) consists of PP.
 13. The tubular bag apparatus as claimed in claim 3, characterized in that flanks of the energy-conducting ribs (183), which flanks are evident in cross section, enclose an angle (α) of 60°.
 14. The tubular bag apparatus as claimed in claim 1, characterized in that the height (h) of the energy-conducting ribs (183) measures 0.3 mm. 